Replacing dial thermostat with Honeywell CM907...

30 Oct 2010
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United Kingdom
I have an old style Honeywell dial thermostat (T6360B). This has three wires connected from my Baxi 105he combi boiler...

Brown from the boiler to terminal 1 in the thermostat
Blue 'switch' wire from the boiler to terminal 3 in the thermostat
Earth to the earch terminal in the thermostat

Am I correct in thinking that the CM907 should just be an easy swap with my T6260B?

There is no earth in the CM907 so I assume I just block that wire off? The wiring diagram for the CM907 shows two connections for a combi boiler to points A and B in the 907.

Can anyone confirm which wire from the T6260B should be connected to point A and which to point B on the CM907 or does it not matter as really it's just a loop for the switch?

Thanks in advance.
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You don't need the earth, there should be a place to put it in the 907 baseplate.
Order of the two other wires doesn't matter. :p

The old thermostat would never have worked well without a neutral wire, by the way, make sure they didn't use the green and yellow for a neutral. It's very common.
Just wired it up, and works perfectly :D Couldn't find an earthing point on the CM907, so just blocked that wire off.

Really strange because I installed it exactly the same way yesterday afternoon, and couldn't get the central heating to work at all. Done it again now and all works perfectly!

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